This invention relates to a method of making 3,5-diaminobenzotrifluoride (DABTF) from 4-chloro-3,5-dinitrobenzotrifluoride (CDNBTF). In particular, it relates to a process in which a solution of CDNBTF is added at a controlled rate to a slurry of a palladium catalyst, magnesium oxide, and an alcohol solvent.
In U.S. patent application Ser. No. 07/685,106, there is described a process for preparing DABTF from CDNBTF by reacting the CDNBTF with hydrogen in the presence of magnesium oxide, a palladium catalyst, and methanol. While that process is successful in the laboratory, it has since been found that upon scaling up to quantities of three gallons or more, the yield falls, the solution becomes dark and gummy, and tars and other undesirable compounds form, making it difficult to isolate the product.
Analysis showed that the starting material, CDNBTF, was reacting with the product, DABTF, to produce a dimer according the equation ##STR1## where R is NH.sub.2 if the reaction is performed in the presence of hydrogen and a Pd/C catalyst and is NO.sub.2 if hydrogen and the Pd/C catalyst are not present. Other undesirable but unidentified compounds also seemed to be present. In addition, dechlorination did not occur completely so that 4-chloro-3,5-diaminobenzotrifluoride (CDABTF) was also formed, apparently due to deactivation of the catalyst.